When a microorganism engineered to intracellularly carry a plasmid that expresses a specific gene is utilized for the production of a useful substance, over-expression of the gene and instability of the plasmid often cause problems. To solve the problems, modifications of genes on a chromosome are carried out as an effective method. Methods involving mutagenic treatments have long been carried out as a chromosomal engineering technique in Escherichia coli. This method is directed to the selection of a desired mutant strain from randomly mutated strains, and requires a great deal of work. In addition, deliberate or rational manipulation is almost impossible.
On the other hand, P1 transduction using P1 phage is known to be the most versatile technique to deliberately and rationally manipulate the chromosome of Escherichia coli [Zinder, N. D. and Lederberg J., J. Bacteriol., 64, 679 (1952)].
Chromosomal manipulation techniques other than P1 transduction are roughly classified into 2 types.
One type is directed to a method which comprises inserting a gene of interest into a plasmid capable of autonomous replication in microorganisms other than Escherichia coli but incapable of autonomous replication in Escherichia coli and transforming Escherichia coli with the plasmid to obtain a strain in which the gene of interest is integrated into its chromosome according to the principle of homologous recombination [A. Chen et al., J. Bacteriol., 176, 1542 (1994)]. However, this method involves a drawback that a desired chromosomal recombinant strain is obtained only at a very low frequency because a plasmid which has been prepared by using a microorganism other than Escherichia coli as a host cell, is decomposed by restriction enzymes within Escherichia coli. 
The other type is directed to the method in which a plasmid being capable of autonomous replication under the normal growth conditions in Escherichia coli K-12 but incapable of autonomous replication under certain conditions such as a high temperature condition is used and a gene of interest is integrated into a chromosome in accordance with the principle of homologous recombination [T. Hashimoto, and M. Sekiguchi, J. Bactereiol., 127, 1561 (1976)].
Escherichia coli that have been widely used in the research and industrial areas include several types such as the K-12, B, and W strains. Many of the genetic recombination techniques have been developed by using the K-12 strain.
Escherichia coli W is suitable for the production of useful substances such as amino acids, etc. [S. Furukawa et al., Appl. Microbiol. Biotechnol., 29, 253 (1988)] and serves many uses in fermentative production as it assimilates sucrose and has been actually subjected to high density cell culture successfully [I. E. Gleiser and S. Bauer, Biotechnol. Bioeng., 23, 1015 (1981)].
The above-mentioned genetic engineering techniques relate to the K-12 strain and no report has so far been made that concerns with microorganisms belonging to the genus Escherichia of the types, different from K-12.